1. Field of the Invention
This invention relates to a method for improving the antibacterial efficacy of an ophthalmic solution, such as a solution used for the care of contact lenses. The solutions are contacted with a resin including antibacterial metal ions in an inorganic carrier.
2. Description of the Art
The majority of commercial ophthalmic solutions, including solutions used for the care of contact lenses, are packaged in dispensing bottles molded from a thermoplastic or thermosetting resin. Such solutions include saline solutions, cleaning solutions which incorporate a cleaning agent and conditioning solutions. Since these solutions come into direct contact with contact lenses or the eye, depending on the intended use of the solution, it is important that the solutions do not become contaminated with microorganisms such as bacteria. The current approach to avoid contamination of the solution involves packaging the solutions under sterile conditions and designing the container to minimize the likelihood of contamination from handling the container. Additionally, many solutions incorporate preservatives to inhibit growth of any microorganisms which may contaminate the solution.
Additionally, contact lens cases designed for storage of contact lenses or for care regimen of the lenses are generally constructed of a thermoplastic or thermosetting resin. When a contact lens is placed in a contact lens cell of the case, it is immersed in a solution. The current approach to inhibit microbial growth in the contact lens cells is to avoid contamination of the case to the extent possible, to cap the cell during use, and to rinse the case between uses. Microbial growth may also be inhibited by the solution placed in the contact lens cell.
It is known that silver ions may be incorporated in ophthalmic solutions to inhibit bacterial or microbial growth. For example, R. Schweisfurth et al. (Contactologia, Vol. 7 D (1985), pages 144-147) disclose antibacterial properties of silver as an agent for storage and disinfection of contact lenses. Additionally, a sodium silver chloride complex (SoluSept.TM., Similasan AG, Switzerland) is described as a preservative for ophthalmic solutions.
Additionally, various agents having antibacterial or antimicrobial properties are known, including agents which can be incorporated in polymer resins, including films, fibers and molded articles. The following patent publications disclose antibacterial zeolites retaining at least one metal ion having antibacterial properties, such as ions of Ag, Cu or Zn, and various polymer articles having antibacterial properties which contain the zeolite: U.S. Pat. No. 4,525,410; U.S. Pat. No. 4,775,585; U.S. Pat. No. 4,906,464; U.S. Pat. No. 4,911,898; U.S. Pat. No. 4,911,899; U.S. Pat. No. 4,938,955; U.S. Pat. No. 4,938,958; U.S. Pat. No. 5,003,638; U.S. Pat. No. 5,064,599; U.S. Pat. No. 5,085,416; abstract of Japan 02/080,442; and abstract of Japan 02/125,717. Other materials which can retain antibacterial metal ions include amorphous aluminosilicate particles, disclosed in U.S. Pat. No. 4,959,268, and hydroxyapatite, such as Apacider.TM. (Sangi Group America Corp., Los Angeles). None of these references suggests the use of the antibacterial agents to improve the efficacy of an ophthalmic solution.